Batteries - Cranking vs. Deep Cycle

drjohn71a · Posted: Tue Aug 21, 2007 9:09 am Post subject:

Thanks guys for the detailed explanation...

I can see now, considering that most boats come with the rapid charge systems would boil the water off if left on. My RV has four of the 6 Volt golf batteries and it's charger boils them down in a few days, while the adjacent starting batteries rarely need any water at all. I guess the starting batteries are not in the shorepower charging loop. And the sporadic, rapid charging of the alternator is not a problem to the starting batteries since it is not on 24/7 as you guys note.

Thanks again for explaining the facts behind the myth!

John

BrentB · Posted: Tue Aug 21, 2007 10:01 am Post subject:

Dr John

Good question and replies from the group. I tend charge batteries using the lowest amp setting and check the water level first. I always thought which may not be correct that using a higher amp setting (rapid) will reduce the battery's life due to the heat. Before Wal Mart, I bought batteries from Sears and they were nearly always generous give me a new replacement battery and a few comments: you need charge the battery after each use, dont drop it, it is sensitive to heat, and it would last longer if it didnt sit idle for extended periods of time.
What a deal! A new battery and friendly advice.

thataway · Posted: Tue Aug 21, 2007 4:58 pm Post subject:

Dr john, a bit off topic, but if you are having problems with the RV--check the charger. Most Rv's have a "converter"--from 30 to 60 amps, with a trickle or small charger. If the voltage is too high, of course you have a water problem. I have 4 golf carts in my RV and keep it pluged in most of the time. You can put a timer on the charger if you want--most of them are plug in, and a regular "out door" timer will work fine.

Also many converters are the Inteli Power series--and if you don't have the "charge Wizard" you can add it. Basically the Charge Wizard, converts the converter to a smart charger and will be much easier on the batteries. Because boats are used differently, and have different 12 volt demands, they do not have "converters --110v AC to 12 V DC--and should not have that problem.

Start with the hydro caps, check the voltage, and go to a "Charge wizard" if you don't have one...

Ashley Lynn · Posted: Tue Aug 21, 2007 5:10 pm Post subject:

If I have two batteries in my 22 footer, should one be a start battery and the second be a deep-cycle? Currently, both batteries are start batteries.
And I might be having a problem with one of them.

Sneaks · Posted: Tue Aug 21, 2007 6:19 pm Post subject:

Bob, if you run both batteries in parallel, you won't just have a problem with one, you'll end up with a problem with both. The defective battery will draw down the good one.

Whenever batteries are wired or switched in parallel, for the longest life they should not only be the same size, they should also be the same manufacturer and preferably built on the same date.

Personally, I hate lead/acid batteries. Cheap, yes. Easy to maintain, yes. Long life, yes. But if they get gassy, the fumes will do a number on anything and everything close by and a small drop of the acid means holes in clothes. Like Linus and dirt, battery acid has always had an affinity for my clothes. 'Specially back in the submarine days....

Don

BrentB · Posted: Tue Aug 21, 2007 10:22 pm Post subject:

mc2w
A class action provides one legal case and isa more efficient legal process and lower legal costs (in theory) and useful tool when dealing with large global corporations.sorry wrong thread
I have 38 open windows

jlastofka · Posted: Tue Aug 21, 2007 11:24 pm Post subject:

As an engineer with an interest in batteries, I've read some technical publications on the subject (not just the popular press). I'd say Bob Austin of Thataway nailed it well in his recent post here.

Running low on water and discharging to a low voltage are two ways to really shorten the life of a lead acid battery. Deep cycle batteries suffer less than cranking batteries, but both are damaged each time you drain them very far.

When you buy a new car and the battery's been discharged on the dealer's lot a couple times, it's already got a reduced life span.

My CD22 with a 90 and a 9.9 has two cranking batteries and a 1/2/both switch. I run one battery or the other on any given day. Not both. The other's in reserve. When I replace them, it will be with marine deep cycle batteries for the durability. Cranking a fuel injected 90 horse engine that starts instantly is not likely to overtax the current supply ability of a deep cycle battery. Why not have the more durable construction of the deep cycle battery? If you're cranking a V-6 or V-8 and it cranks a while, maybe a starting battery is justified.

A really good gizmo is an integrating amp hour meter, like those made by Xantrex. West Marine and lots of sources sell them. There's a two channel version also. I have one in my sailboat. It constantly adds and subtracts the current being drawn from and charged into the battery and gives you a running total of the remaining amp hours in the battery. Plus it's a very accurate volt and amp meter. You can really monitor your batteries, lights and electronics with this device. It's what the serious cruising sailors use.

If you run your engine often and only drain the batteries a little once in a while, you don't need to monitor much. But if you're camping overnight and running the batteries down using lights, radios, refrigerators, etc. you really should have such a meter.

Starting batteries are optimized for short bursts of high current with less voltage drop during cranking. Deep cycle batteries are optimized to better resist damage when discharged somewhat deeply, like to the 50% or 30% level once in a while. Starting batteries don't hold up well when treated like that.

Jeff